Current as of September 28, 2026. General information, not medical advice.
Short answer: Hematocrit is the number that actually changes management. Four different authorities set four different action thresholds, and the FDA label sets none at all. The common ground: check it before you start, check it again at three to six months, then at least yearly, and above 54 percent everybody says stop.
The disagreement nobody mentions
Here is what the major bodies actually say, side by side.
Endocrine Society, 2018. Above 48 percent at baseline is a relative contraindication, above 50 at altitude. On therapy, above 54 percent: stop until it comes down to a safe level, evaluate for hypoxia and sleep apnea, then restart at a lower dose.
AUA, published 2018 and validity confirmed in 2024. Above 50 percent at baseline, consider withholding until the cause is investigated. On therapy, 54 percent or above warrants intervention such as dose reduction or temporary discontinuation.
Defense Health Agency, September 2026. Above 50 at baseline, do not start until the cause is explained. On therapy, above 52 percent means blood donation or therapeutic phlebotomy, reducing the dose, or withholding. At 54 or above, stop until it is below 50.
VA Pharmacy Benefits Management, January 2026. Above 48 at baseline. Dose adjustments above 51. Stop above 54.
The FDA label. Check hematocrit before starting. If it becomes elevated, stop until it decreases to an acceptable concentration. No number given.
So if a clinic tells you there is one standard threshold, they have read one document.
The part a government guideline admitted out loud
The DoD guideline says something you will not hear in a sales call, and it is worth quoting exactly:
The 54 percent action threshold is derived by extrapolation from epidemiologic data on primary polycythemia and is not established by outcome studies in men receiving testosterone therapy. No prospective or randomized study has demonstrated that testosterone-associated erythrocytosis causes thrombotic events. It is retained as a conservative action threshold pending better evidence, and the service member should be so informed.
The Endocrine Society says the same thing in its own way: the hematocrit level at which the risk of neuro-occlusive or cardiovascular events increases is not known.
That does not mean ignore the number. It means the number is a safety margin, not a cliff edge, and you deserve to be told which one it is.
Worth knowing on formulation: injectable testosterone is associated with the greatest treatment-induced rise in hemoglobin and hematocrit.
The rest of the panel
Before you start. Two morning fasting total testosterone levels on separate days, because a single low reading is not a diagnosis. LH and FSH, which tell you whether the problem is in the testes or the pituitary. Hemoglobin and hematocrit. Prolactin. PSA and a discussion about it if you are over 40. Very low levels, under about 150, deserve evaluation for a pituitary cause.
After you start. The schedules differ slightly. The DoD guideline wants trough testosterone and hematocrit at four to six weeks after starting or any dose change, then every six months, with PSA yearly over 40 and blood pressure at every visit. The Endocrine Society wants evaluation at three to twelve months then annually, with hematocrit at baseline, three to six months, then annually. The AUA wants testosterone every six to twelve months and hematocrit kept below 54.
Targets. The AUA aims for the middle of the normal range, roughly 450 to 600 ng/dL. The DoD guideline targets a trough of 300 to 600. The Endocrine Society says for injections, measure midway between doses and adjust if that mid-interval level is above 600 or below 350.
PSA rules. Urological referral for a confirmed rise of more than 1.4 ng/mL above baseline, a confirmed PSA above 4.0, or an abnormal exam. The DoD guideline is tighter: referral above 3.0, or a rise above 1.0 in twelve months.
Two numbers that should stop a prescription
Roughly 30 percent of men with an initial low value are normal on repeat testing. That is the DoD guideline's own figure, and it is the single best argument for drawing twice.
And the timing rule that goes with it: a specimen drawn within 30 days of training involving extreme physical or mental stress or sleep deprivation is not interpretable and will not be used. Hard training, short sleep and a caloric deficit suppress the axis temporarily. That is not hypogonadism, and treating it as such suppresses your own production and compromises fertility for no reason.
What high hematocrit means in practice
Your blood gets thicker. Management is unglamorous and it works: reduce the dose, change the formulation, donate blood or get a therapeutic phlebotomy, treat the sleep apnea that is often sitting underneath it, and stop entirely if it stays high.
Sleep apnea deserves its own line. It drives hematocrit up on its own, it is common in exactly the population seeking TRT, and it is frequently undiagnosed.
Questions people actually ask
What hematocrit is too high on TRT? Above 54 percent, every authority says act, usually by stopping until it comes down. Action starts earlier in some guidelines: above 51 at the VA, above 52 in the DoD guideline.
How often should my blood be checked? At minimum before starting, again at three to six months, then at least annually. The DoD schedule is tighter at four to six weeks after any dose change, then every six months.
Is high hematocrit actually dangerous? The threshold is precautionary. The DoD guideline states no prospective or randomized study has shown testosterone-associated erythrocytosis causes clots. Nobody knows the exact level where risk rises, which is why the margin is conservative.
Do I need PSA testing? Over 40, yes, before starting and then periodically, with referral on a meaningful rise.
Can one low lab diagnose me? No. About 30 percent of men with one low value are normal on a repeat.
Where we fit
This whole article is our intake. Two morning fasting draws on separate days before anything is prescribed, LH and FSH every time, prolactin, hematocrit before and on schedule after, PSA where age-appropriate, and blood pressure at every visit.
We also read the timing. If you just came off a selection course or a deployment work-up, we will tell you the lab is not interpretable yet rather than treating it.
Discounted pricing for military, law enforcement and first responders. Request a consultation at hewhealth.com or call (850) 820-8850.
Hew Health, LLC is a private medical practice. General information as of September 28, 2026, not medical advice. Testosterone is a Schedule III controlled substance. FDA-approved testosterone products are indicated for men with low testosterone caused by an associated medical condition, and none are approved for men with low testosterone who lack an associated medical condition.
Sources: Endocrine Society clinical practice guideline, 2018 (PMID 29562364), table 9 and recommendation 3.2. AUA Testosterone Deficiency Guideline, published 2018, reviewed and validity confirmed 2024 (PMID 29601923), statements 11, 12, 22, 30 and table 7. DHA clinical practice guideline, Testosterone Deficiency in the Male Service Member, September 17, 2026. VA PBM, Evaluation for and Management of Males with Low Testosterone, January 2026. FDA prescribing information, AndroGel revised October 2025 and AZMIRO revised July 2025.